Electrical interconnects for battery cells

ABSTRACT

A battery pack includes a pouch cell having electrode tabs extending therefrom, each of the tabs defining perforations, a bus bar in contact with the tabs, and respective agglomerations of mechanically bound solid metal particles each filling one of the perforations to mechanically bind and electrically connect the tabs to the bus bar.

TECHNICAL FIELD

The disclosure relates to ion pouch battery cells and methods ofproducing the same.

BACKGROUND

Lithium ion pouch cells have been utilized in a variety of industriesincluding automotive applications. The pouch cell designs are attractivedue to their reduced weight and cost as well as optimized packagingefficiency at the battery level, higher specific density, and highervoltage output per cell than many other systems. Thus, lithium ion powersystems have become the primary choice for many applications.Traditional electrical interconnects of the pouch cells are formed asfastened threaded studs or ultrasonically welded tabs which mayexperience mechanical inconsistencies, high contact resistance, bondnon-uniformities, and other issues. Additionally, either solution isproblematic with regard to connecting a bus bar with tabs formed fromdissimilar metals.

Alternative methods such as thermal spray deposition have been developedto provide battery interconnects. Yet, these methods such as arc sprayor plasma spray subject the pouch cell to temperatures of up to 20,000°C. Additionally, bonds produced by thermal spray deposition may sufferfrom oxide depositions.

SUMMARY

In at least one embodiment, a battery pack is disclosed. The batterypack includes a pouch cell having electrode tabs extending therefrom,each of the tabs defining perforations. The battery pack furtherincludes a bus bar in contact with the tabs, and respectiveagglomerations of mechanically bound solid metal particles each fillingone of the perforations to mechanically bind and electrically connectthe tabs to the bus bar. Each tab may include at least one row ofperforations. The perforations may be circular. The perforations withinat least one of the tabs may have different dimensions. The perforationsmay be arranged in a regular pattern. The agglomerations may cover atleast a portion of the tabs. The agglomerations may be free of voids,oxide inclusions, or both. Each of the particles may have a discretecrystalline structure.

In another embodiment, a battery pack is disclosed. The battery packincludes a bus bar and a pair of pouch cells. The pouch cells each havea castellated tab extending therefrom, and are arranged adjacent to oneanother such that the castellated tabs are aligned and interdigitate tocontact the bus bar. The battery pack further includes an agglomerationof solid metal particles mechanically bound to each other, thecastellated tabs, and the bus bar to electrically connect thecastellated tabs to the bus bar. The first castellated tab may include apair of prongs. The adjacent castellated tabs may include prongs thatare in contact with one another. The prongs of a first castellated tabmay have different dimensions than the prongs of a second castellatedtab. The tabs may include at least one perforation each. Theagglomeration may be free of voids, oxide inclusions, or both.

In yet another embodiment, a battery pack is disclosed. The battery packmay include a bus bar and a plurality of pouch cells. The pouch cellsmay each have a tab extending therefrom to a different height ascompared with other of the pouch cells, and be arranged adjacent to oneanother such that the tabs are aligned and form a terrace with each ofthe tabs contacting the bus bar. The battery pack may further includerespective agglomerations of mechanically bound solid metal particleslayered over an end of each of the tabs and a portion of the bus bar toelectrically connect the tabs to the bus bar. A height of the first tabmay be at least 50% of a height of a second tab. The plurality of pouchcells may include at least three cells. The tabs may have a differentchemical composition. At least some of the tabs may have a width smallerthan a width of the bus bar. The agglomerations may be free of voids,oxide inclusions, or both.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an exploded view of individual layers within a pouchcell battery depicted in FIG. 1B;

FIG. 1B depicts a perspective view of an example pouch cell battery;

FIG. 2 depicts a perspective view of an example pouch cell connected toan example bus bar according to one or more embodiments;

FIGS. 3A-3C depict detailed example perforation patterns on tabsdepicted in FIG. 2;

FIG. 4A depicts a perspective view of a portion of an example batterypack having castellated tabs;

FIG. 4B shows an alternative embodiment of the battery pack withcastellated tabs depicted in FIG. 4A;

FIG. 4C depicts the battery pack of FIG. 4A or 4B with castellated tabsconnected to the bus bar;

FIG. 5 shows a perspective view of a portion of an alternative examplebattery pack having tabs connected to the bus bar forming a terrace;

FIG. 6 shows a schematic view of an example cold spray system includingan agglomerate-substrate interface produced in a cold spray system;

FIGS. 7A-7D depict changes in a particle-substrate interface upon impactof a solid particle with a surface of a substrate during a cold spraydeposition process;

FIG. 8 depicts a perspective schematic view of a coating-substrateinterface produced by a thermal spray deposition process; and

FIG. 9 depicts a schematic detailed view of the agglomerate-substrateinterface forming interconnects depicted in FIGS. 2, 4C, and 5.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments may take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures may be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

Except where expressly indicated, all numerical quantities in thisdescription indicating dimensions or material properties are to beunderstood as modified by the word “about” in describing the broadestscope of the present disclosure.

The first definition of an acronym or other abbreviation applies to allsubsequent uses herein of the same abbreviation and applies mutatismutandis to normal grammatical variations of the initially definedabbreviation. Unless expressly stated to the contrary, measurement of aproperty is determined by the same technique as previously or laterreferenced for the same property.

The description of a group or class of materials as suitable for a givenpurpose in connection with one or more embodiments of the presentinvention implies that mixtures of any two or more of the members of thegroup or class are suitable. Description of constituents in chemicalterms refers to the constituents at the time of addition to anycombination specified in the description, and does not necessarilypreclude chemical interactions among constituents of the mixture oncemixed. The first definition of an acronym or other abbreviation appliesto all subsequent uses herein of the same abbreviation and appliesmutatis mutandis to normal grammatical variations of the initiallydefined abbreviation. Unless expressly stated to the contrary,measurement of a property is determined by the same technique aspreviously or later referenced for the same property.

With mass-production of batteries, a variety of battery formats havebeen developed. Example battery formats include cylindrical cells,button cells, prismatic cells, and pouch cells. The pouch cell designrepresents an efficient use of space and achieves about 90-95% packagingefficiency. Instead of using a metallic cylinder and glass-to-metalelectrical feed-through, conductive foil tabs are typically welded tothe electrodes and are fully sealed while extending outside of thepouch. By eliminating a metal enclosure, the weight of the pouch cell isreduced.

While a pouch cell is a lightweight solution to the battery design, thepouch format presents a number of considerations such as requirement forsupport and space to expand. Additional concerns are exposure tohumidity and high temperatures which may shorten life of the cell.Swelling represents yet another concern, for example swelling by up to8-10% over 500 cycles may be typical with some types of pouch cells.Yet, pouch cells have become popular, especially in the same performancecriteria as cylindrical cells. Pouch cells have been successfullyutilized in consumer, military, as well as automotive applications.Relatively large flat pouch cell packs have been applied in electricpowertrains and Energy Storage Systems. Relatively small pouch cellshave been used for portable applications with high load currentrequirements.

An example lithium-ion pouch cell 10 is depicted in FIGS. 1A and 1B. Ascan be seen in FIGS. 1A and 1B, a pouch cell 10 has a laminatedarchitecture in a pouch 12. The pouch 12 includes a cathode 14 with abattery tab or terminal 16, an anode 18 with a battery tab or terminal20, and a separator 22 sandwiched between the cathode 14 and the anode18. After the laminated layers 14, 18, 22 are assembled together andinserted into the pouch 12, the pouch 12 is filled with electrolyte andsubsequently sealed in such as a way that the tabs 16 and 20 are outsideof the pouch 12.

The pouch cells 10 are typically lithium-ion batteries with liquidelectrolyte. The electrolyte may be gelled via an addition of a polymeradditive. The cells 10 are also called LiPo for lithium polymer. Yet, avariety of alternative lithium-ion electrochemistries may be employed.The tabs, or terminals, 16, 20, of the lithium-ion pouch cell 10 usuallyhave different chemistries because they are internally connected to thecathode 14 and anode 18 which are formed from dissimilar metals. Thecurrent collectors, the cathode 14 and the anode 18, are typically madefrom copper, aluminum, or nickel foils. The tabs 16, 20 are usuallyformed from the same metal as the respective electrode 14, 18 to avoidcreation of a galvanic cell between the electrode and the tabs. Yet, thepresence of tabs 16, 20 formed from dissimilar metals presents achallenge when the tabs 16, 20 are to be connected to a bus bar due tometal incompatibility which may lead to higher incidence of corrosion,increased resistance, and a lack of joint robustness.

The electrode interconnects between the tabs and the bus bar havetraditionally consisted or either fastened threaded studs orultrasonically welded tabs. The latter exhibits a number of issues suchas inconsistent bond uniformity and apparatus (horn and anvil) fatigueissues. Using the fastened threaded studs, on the other hand, may resultin mechanical failure and high contact resistance.

To avoid the above-mentioned disadvantages, thermal spray depositiontechniques have been utilized to form the interconnects between the busbar and the electrode terminals. Many of the methods utilizehigh-temperature thermal spray processes to deposit the solderablematerial. The thermal spray deposition techniques are generallyprocesses enabling layering of a wide range of feedstock material on asubstrate at high deposition rates. Yet, the methods employ relativelyhigh temperatures causing the material to melt. In thermal sprayprocesses, the bonding mechanism is mechanical interlocking, and thebonding may be improved by increasing temperature or particlevelocities. But the high processing temperatures generally increase theamount of oxides embedded in the coating, reduce the coating'sperformance for structural applications, and potentially damage thecell. For example, the cell separator 22 usually has a relatively lowtemperature tolerance which limits the applicable processes. Examplethermal spray techniques and the temperature ranges typically associatedwith them include a plasma spray process with temperatures between9,727° C. (10,000 K) and 19,727° C. (20,000 K), wire arc withtemperatures of about 14,727° C. (15,000 K), detonation gun depositionutilizing temperatures of about 5,227° C. (5,500 K), or high velocityoxyfuel deposition (HVOF) with temperatures of about 5,227° C. (5,500K).

Therefore, it would be desirable to provide electrode terminal-bus barinterconnects applied in a way which would eliminate high-wear toolingcomponents such as horn and anvil from the assembly process, alleviateinterfacial debonding and through-thickness fractures which are typicalfor ultrasonic welding, reduce degradation and parasitic inductance byproducing dense, layered coatings with low porosity and oxidation, andprovide superior corrosion resistance and low electrical resistancewhile maintaining such process temperatures which would preventdestruction of the cell or creation of oxide inclusions.

In one or more embodiments, depicted in FIG. 2, a battery pack 124 isdisclosed. The battery pack includes a pouch cell 100 with the cathodetab 116 and an anode tab 120 extending from the pouch 112. The tabs 116,120 are aligned with a bus bar 130 such that the tabs 116, 120 are incontact with the bus bar 130. The tabs 116, 120 may be made from copper,aluminum, nickel, zinc, lead, the like, or a combination thereof. Aprotective layer may be formed on the surface of the one or more tabs topromote bonding of the tabs to the busbar. The protective layer mayinclude nickel, titanium, zinc, silver, gold, tin, the like, or acombination thereof. The tab 116 may be made from the same or differentmaterial as the tab 120. The surface of either or both of the tabs 116,120 may be at least partially smooth or textured to increase surfacearea for the bond between the tabs 116, 120 and the bus bar 130.

The tabs 116, 120 include one or more perforations 126. Each perforation126 is filled with an agglomeration 132 of mechanically bound solidmetal particles which facilitate bonding of the tabs 116, 120 to the busbar 130. The perforations 126 may be partially filled with theagglomerated material 132 such that at least a portion of a perforation126 remains free of the agglomerated material 132. Alternatively, theentire surface area of the busbar 130 in contact with and outlined bythe perforation 126 may be covered with the agglomerated material 132.The agglomerations 132 may cover at least a portion of the tabs 116,120. The perforations 126 may be filled with the metal particles formingagglomerations 132 in such a way that respective agglomerations 132 arenot in contact with each other. Alternatively still, an agglomeration126 may fill and/or cover more than one perforation 126. Anagglomeration 132 may have a thickness that does not exceed a thicknessof the tab 116, 120. Alternatively, the agglomeration 132 may have agreater thickness than the thickness of the tab 116, 120. Anagglomeration 132 may have a diameter which does not exceed a diameterof a perforation 126. Alternatively, a diameter of an agglomeration 132may be greater than a diameter of the perforation 126.

The tabs described herein may include one or more perforations 126. Aplurality of perforations 126 may contribute to better heat conductancethan presence of just a single perforation 126. Additionally, providinga plurality of perforations 126 increases the number of sites for thedeposition of agglomerations 132, which in turn contributes to increasedjoint robustness and lessens a chance of attachment failure between thetabs and the bus bar.

The tabs 116, 120 may include the same or different number ofperforations 126 having the same or different shape, cross-section,dimensions, orientation, and other properties. Example perforations 126are depicted in FIGS. 3A-3C. While FIGS. 3A-3C depict the tab 116 andperforations 126, the tab 116 and perforations 126 are just examples,and the description is applicable to any tab and perforation describedherein. As can be seen in FIG. 3A, the tab 116 may include perforations126 which are regularly spaced apart from each other. The perforations126 may have a cross section which is a circle, an oval, a square, arectangle, a pentagon, a heptagon, an octagon, a nonagon, a trapezium, atriangle, a star, a quatrefoil, a kite, a regular shape, an irregularshape, a symmetrical shape, an asymmetrical shape, the like, or acombination thereof. The perforations 126 may have a perimeter 128 whichis smooth, rugged, ridged, coarse, jagged, the like, or a combinationthereof. In one or more embodiments, some of the perforations 126 mayhave a perimeter 128 which is not smooth. Alternatively, someperforations 126 may include smooth portions and coarse portions. Thecoarseness may provide additional surface area for bonding. An examplesmooth edge 128 may be seen in FIG. 3A, and an example jagged edge 128can be seen in FIG. 3B. The tab 116 may include one or more rows ofperforations 126. Single-row perforation tabs 116 are depicted in FIGS.3A and 3B while an example of a multi-row perforation tab 116 isdepicted in FIG. 3C.

The perforations 126 may constitute about less than 5%, 5%, 10%, 20%,30%, 140%, 50% or more of the surface area of the tab surface area. Thedimensions of a perforation 126 may differ from dimensions of at leastone other perforation 126. Alternatively, all perforations 126 may havethe same dimensions. All of the tabs 116, 120 may have the same patternof perforations 126. The pattern may be regular or irregular,symmetrical, or asymmetrical. Alternatively, a tab may include adifferent pattern of perforations 126 than at least one other tab.Providing the same pattern of perforations 126 for all the tabs maysimplify the manufacturing process. Yet, customization is contemplatedand varying patterns may be beneficial, for example, if respective tabsvary in thickness and/or composition of material. The perforations 126in the tabs may be provided by a number of techniques, for example bystamping, punching, blanking, embossing, by another type ofpre-handling, or a combination thereof.

In another embodiment, depicted in FIGS. 4A-4C, a battery pack 224 isdisclosed. The battery pack 224 includes pouch cells 200. The pouchcells 200 may form a pair. Alternatively, the battery pack 224 mayinclude more than two pouch cells 200. Each pouch cell 200 has acastellated tab 208 extending therefrom. The castellated tab 208 may bea cathode tab 216 or an anode tab 218. Alternatively, just one of thecathode and anode tabs 216, 220 may be a castellated tab 208 while theother tab is free of a castellated design.

The castellated tab 208 has one or more prongs 238 separated from oneanother with a gap. The overall profile of the castellated tab 208resembles a castle having battlements. The number, shape, orientation,location, and dimensions, of the prongs 238 and gaps 207 may differ. Forexample, as can be seen in FIG. 4A, a first castellated tab 208 has twoprongs 238 while the second castellated tab 208 has three prongs 238.Any number of prongs 208 is contemplated as long as the prongs ofadjacent tabs 208 interdigitate to contact the bus bar 230. The prongs230 may have the same or different dimensions, shape, or the like. Forexample, the prongs 238 may have rounded edges. Alternatively, the edgesof the prongs 238 may be even, uneven, regular, irregular, jagged,curved, pointed, ridged, serrated, smooth, the like, or a combinationthereof. As can be seen in FIG. 4B, each castellated tab may includethree respective prongs. The first tab 208′ includes three prongs 238′having the same dimensions and shape, each prong 238′ having a generallyrectangular shape with a flat top and wavy sides having a plurality ofcrests and troughs. The second tab 208″ has three prongs 238″, two ofwhich have smaller height than the third prong 238″ and the prongs 238′of the first tab 208′. The prongs 238″ of the second tab 208″ facing theprongs 238′ of the first tab 208′ have wavy sides with crestscorresponding to troughs of the prongs 238′ and troughs corresponding tocrests of the prongs 238′. The above-named properties of the prongs238′, 238″ of both tabs 208′, 208″ have to be such as to enable thecastellated tabs 208 to interdigitate and contact the bus bar 230.

Alternatively, the prongs 238 may have a square or rectangular shapewith pointed corners. The height and/or width of multiple prongs 238 maybe the same or the height, width, or both of a prong 238 may differ fromat least one other prong 238. For example the prongs 238 located in thecenter of a tab 208 may have greater dimensions than the remainingprongs 238. Any dimensions, shape, orientation, and location of a prong238 within the tab 208 is contemplated as long as the at least two tabs208 are castellated and interdigitate.

As is depicted in FIGS. 4A and 4B with respect to two example tabs 208in contact with each other, the lower portions 242 of the tabs 208 arealigned with each other and layered such that the lower portions 242 ofthe tabs 208 are in direct contact with each other. On the other hand,the prongs 238, forming the top portions 244 of the tabs 208, are not incontact with each other. Instead, the prongs 238 interdigitate andbecome intertwined like fingers of folded hands while maintaining a gap240 between the interdigitated prongs 238 of the two tabs 208 incontact. In one or more embodiments, at least some of the prongs 238 mayoverlap each other. The tabs 208 may include one or more perforations126 described above.

The top and/or side edge(s) of at least some of the pouches 212 may, butnot have to be flush with each other. For example, as can be seen inFIG. 4A-4C, the first and second pouches' top and side edges are flushwith each other.

An agglomeration 232 of solid metal particles is mechanically bound tothe castellated tabs 208 and to the bus bar 230. The agglomeration 232thus forms interconnects 234 which electrically connect the tabs 208 tothe bus bar 230. In one or more embodiments, depicted in FIG. 4C, theinterconnects 234 are formed from a single elongated stripe of theagglomerated material 232 creating a coating or an overlay 236. Theagglomeration 232 may be continuous or discontinuous. Alternatively, theinterconnects 234 may include more than one respective agglomeration232. For example, a set of respective agglomerations 232 may be appliedover the layered castellated tabs 208 and the bus bar 230. An exampleapplication of the agglomerations 232 may include a set of respectiveagglomerations forming stripes filling the one or more gaps 240 betweenthe respective interdigitated prongs 238 of at least two tabs 208.Alternatively still, individual agglomerations 238 covering the gaps 240may be combined with one or more elongated agglomeration 238 overlays.

In yet another embodiment, depicted in FIG. 5, a battery pack 324 isdisclosed. The battery pack 324 includes a plurality of pouch cells 300.Each pouch cell 300 has tabs 308 extending therefrom to a differentheight than other tabs 308 of other pouch cells 300. The pouch cells 300are arranged adjacent to one another such that the tabs 308 of variousheights are aligned and form a terrace 342 with each of the tabs 308contacting the bus bar 330. The terrace 342 resembles flat areas createdon a side of a hill to grow crops such as terraced rice paddies. Theindividual flat areas are formed from respective agglomerations ofmechanically bound solid metal particles which are layered over an endportion 346 of each of the tabs 308 and a portion of the bus bar 330.The end portion 346 may include about less than 5%, 5%, 10%, 20%, 30%,40%, less than 50% of the surface area of the respective tab 308. Theagglomerations 323 form interconnects electrically connecting the tabs308 to the bus bar 330.

As is further depicted in FIG. 5, the terrace 342 includes a first tab308′ or the first pouch cell 300′, the tab 308′ being aligned with thebus bar 330 such that the bus bar 330 and the tab 308′ lay flat againsteach other. An agglomeration 323′ connects the first tab 308′ with thebus bar 330. The second tab 308″ has a greater height than the first tab308′ such that the second tab 308′ contacts the bus bar 330 while beingaligned with the first tab 308′. An agglomeration 323″ is deposited overthe bus bar 330 and the top portion of the second tab 308″. The thirdagglomeration 323″ is likewise deposited over the bus bar 330 and thethird tab 308″, which has a greater height than the second tab 308″,such that the third tab 308″ contacts the bus bar 330. The top and/orside edge(s) of at least some of the pouches 312 may, but do not have tobe flush with each other. For example, as can be seen in FIG. 5, thefirst, second, and third pouches' top and side edges are flush with eachother.

While the depicted embodiment in FIG. 5 shows three agglomeration layers323′, 323″, and 323″, greater or smaller number of agglomeration layersis contemplated and depends on the number of cells 300 to be connectedwithin the battery pack 324. Likewise, dimensions and shape of the tabs308 and the dimensions, shape, and location or the agglomerations 323may be the same or differ throughout the battery pack 324 and may bethose described above. The differing dimensions may be the height,width, thickness, or a combination thereof. The dimensions of the tabs308 may differ as long as all the tabs 308 have a direct contact withthe bus bar 330. The height, width, and/or thickness of the tabs 308 maybe smaller than the height, width, and/or thickness of the bus bar 330.The height, width, and/or thickness difference between the smallest andthe greatest tab 308 may be about less than 10%, 10%, 20%, 30%, 40%,50%, 60% or more. The location of the agglomerations 323 may be at thetop portion 346 of the respective tab 308, at one or more side edges 348of the tab 308, or both. The agglomeration 323 may be continuous ordiscontinuous.

For example, the height of the tabs 308 may differ, as was describedabove with respect to FIG. 5. Alternatively, the height of therespective tabs 308 may be the same and the width may differ such thatthe tab 308′ of the pouch cell 300 located closest to the bus bar 330has the smallest width. An agglomeration 323 is deposited over the sideedges 348 and/or the top edge/end portion 346 of the tab 308′. A secondtab 308′ having a greater width than the first tab 308′ is aligned withthe first tab 308′, and an agglomeration is deposited over the side edge348, and optionally over the top edge/end portion 346, of the second tab308″. An additional tab 308″ or more tabs 308, each with an increasingwidth, may be placed on top of the preceding tab and layered over withan agglomeration. A final agglomeration layer may be deposited once allof the tabs 308 have been layered and secured to the bus bar 330 via theagglomerations 323.

The agglomerations 132, 232, 332 form the battery interconnects 134,234, 334. The interconnects are thus formed as an agglomeration of solidparticles mechanically bound to each other and the substrate via plasticdeformation. The substrate includes the bus bar 130, 230, 330 and thetabs 116, 216, 316, 120, 220, 320. The agglomeration of particles may beformed using a cold spray deposition method also called gas dynamic coldspray (GDCS). The cold spray deposition is an impact consolidationmethod. The cold spray deposition differs from hot spray processesmentioned above by using a much lower temperature such as ambienttemperature of about 24° C. (297.15 K) to about 80° C. (353.15 K) suchthat the material which is being deposited onto a substrate remains in acompliant, but solid state. The temperature may be increased beyond therange named above to achieve higher pliability and softness of theparticles as long as the elevated temperature is below the melting pointof the particles and the substrate. Thus, the cold spray deposition is aprocess of depositing particles without a phase change. Since there isno phase change, all particles in the agglomeration have the samethermo-mechanical history which leads to uniform properties of theinterconnects.

During a cold spray deposition process, powdered metal particles aredeposited on a substrate by ballistic impingement at supersonicvelocities to form a layered coating or a free-form structure. Anexemple schematic depiction of a cold spray system 50 can be seen inFIG. 6. The system 50 includes a powder feeder 52 for accepting a powderfeed 54 having particle size of about 1-100 μm in diameter. The feed 54may be a powder including metals such as Mg, Al, Si, Sc, Ti, V, Cr, Mn,Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Rh, Pd, Ag, In, Sn, Hf, Ta, W, Ir, Pt,Au, Re, polymers, ceramics, composite materials, metal matrix compositematerials, nanocrystalline materials, or a mixture thereof. Individualparticles of the feed may be soft, hard, rigid, smooth, rough, or thelike.

Example powder feed rate may be 1-10 pounds/hour. The system 50 furtherincludes a gas inlet 56 for supplying gas capable of entraining thesolid particles 58. The gas may be, for example, N₂, He, their mixture,or the like. A heater 60 is provided for heating the entraining gas toabout 100-500° C. to increase ductility of the particles 58 to bedeposited onto the substrate 62. The gas flow rate may be about 30-100CFM. The powder feed 54 is inserted at high pressure and temperature atthe entrance of the supersonic nozzle 64. The gas expands andaccelerates through the nozzle 64 as its temperature decreases. Rapidchanges take place at the nozzle throat 66, where gas supersonicvelocity is reached. The velocity and temperature of the solid particles58 approach gas values as heat transfer occurs.

The high pressure and temperature produced within the cold spray system50 are capable of yielding supersonic gas velocities such as about300-1500 m/s and high particle acceleration within the gas stream 68.The solid particles 58 are entrained within the gas stream 68 anddirected towards the substrate 62, where they embed on impact and form astrong bond with the surface of the substrate 62. The kinetic energy ofthe particles 58, supplied by the expansion of the gas, is converted toplastic deformation energy during bonding. To achieve particleconsolidation with the surface, a critical velocity must be reachedbefore impact of the particles 58 with the substrate 62. The criticalvelocity differs depending on the feed type. Because the particles 58remain in their solid state and undergo plastic deformation, their shapemay become lenticular on impact, as is depicted in FIGS. 7A-7D.

FIGS. 7A-7D illustrate a sequence of changes at the particle-substrateinterface 70 upon the solid particle's 58 impact with the surface of thesubstrate 62. As can be seen in the FIGS. 7A-7D, when the particle 58encounters the substrate 62, the particle 58 flattens while a crater 72forms in the substrate 62. The depth and width of the crater 72increases with time such that w₁<w₂ and h₁<h₂. At the same time, thetemperature at the impact zone rises, the rise being concentrated at theparticle-surface interface 70. Yet, the discrete crystalline structureof the solid particle 58 is preserved upon impact. The resultingconnection between the solid particles 58 and the substrate 62 producesa mechanical mixing at the particle-substrate interface 70 similar toexplosive bonding.

In contrast to the cold spray deposited particles 58 depicted in FIGS.7A-7D, a coating-substrate interface 80 of thermally sprayed moltenparticles 82 deposited on a substrate 84 is illustrated in FIG. 8. Theresulting structure includes molten particles/material 82, voids 86, aswell as oxide inclusions 88 and unmelted particles 90.

Advantageously, the mechanical mixing of cold spray deposition does notallow for presence of voids, typically associated with thecoating-substrate interface 80 created by the thermal spray processes,at the particle-substrate interface 70. An example consolidated depositof solid powder particles 58 forming the interconnects, describedherein, as a void-free structure can be seen in FIG. 9. As can befurther seen in FIG. 9, the thickness of the deposited particle layer,or the agglomerate 132, may be increased by supplying an additionalamount of solid particles 58. In the formed agglomeration 132, theadditional amount of particles 58 mechanically mix with the alreadydeposited solid particles 58. No voids are created within theagglomerate 132. The particle-substrate interface 70 as well as theparticle-particle interface 74 are free of voids and oxide inclusions.

Since the interconnects 134, 234, 334 may be made from materials thatare sensitive to the presence of oxygen and will readily oxidize atelevated temperatures, such as copper and aluminum, the thermal sprayprocesses may produce interconnects of inferior quality. Yet, melting ofthe particles that occurs during most thermal spray processes, and whichmay result in oxidation of the coating and the substrate and thus lowerperformance of the module, is not present in the cold spray process. Theagglomerate 132 and the particle-substrate interface 70, produced duringthe cold spray process, are thus free of oxide inclusions which couldotherwise decrease the adhesive and cohesive strength of the coating 136forming the interconnects 134, 234, 334. The interconnects 134, 234, 334are thus deposited as a dense coating 136 with low oxide content of lessthan about 0.3 to 0.5%. The coating 136 is a non-porous or low-porousstructure having porosity of less than about 0.5% to 2%. Yet, thecoating 136 has physical characteristics such as strength comparable orsurpassing those of some wrought materials. Exemplary adhesive strengthof the particles 58 to one another and to the substrate 62 may be about10 to 60 MPa or more, about 15 to 40 MPa or more, or about 15 to 25 MPaor more.

In one or more embodiments, a method for direct cold spray deposition ofelectrical interconnects 134 is disclosed. The method for producinginterconnects 134, depicted in FIG. 2, includes providing a pouch cell100 with tabs 116, 120. The tabs 116, 120 are perforated. The methodcontemplates perforating the tabs 116, 120 by one or more processesdescribed above. The perforated tabs 116, 120 are then aligned with thebus bar 130. The alignment results in the majority of the surface areaof the tabs 116, 120 being in direct contact with the surface area ofthe bus bar 130. The method further includes forming agglomerations 132of solid metal particles within the perforations 126, as was describedabove. The solid particles are mechanically intermixed with thesubstrate, the bus bar 130, the agglomerations 132 being free of voidsand/or oxide inclusions. The agglomerations 132 may form one or morelayers of varying dimensions, shapes, locations, configurations, or acombination thereof. To prevent deposition of the agglomerations 132elsewhere, a shield or a mask may be applied over the cell 200, theshield or mask preventing deposition of the sprayed material outside ofthe target areas. The agglomerations 132 forming the interconnects 134may be cold spray deposited by the method described above.

The dimensions of the deposited material such as height, width, andthickness of the individual interconnects 134 may be varied according tothe needs of a particular application. Likewise, at least some of theinterconnects 134 may be made from a different material than theremaining interconnects 134. All of the interconnects 134 may be formedat the same time, or a first portion of interconnects 134 may be formedprior to cold spray deposition of a second portion of the interconnects134. The cold-sprayed interconnects 134 may be planar, compactstructures applied as a relatively flat coating 30 and thus may be morespace-efficient than the welded or threaded stud interconnects.

In another embodiment, a method for forming interconnects 234, depictedin FIGS. 4A-4C, is disclosed. The method includes providing a pluralityof cells 200 having castellated tabs 208, as was described above. Themethod further includes aligning the castellated tabs 208 with the busbar 230. The alignment may be such that lower portions 242 of the tabs208 overlap while the top portions 244 having prongs 238 interdigitate.Aligning may include placing the cells' top and/or side edge(s) flushwith one another. The interdigitated prongs 238 may be aligned such thattheir sides are in contact with adjacent prongs 238. Alternatively, themethod may include interdigitating the tabs 238 in such a way that therespective prongs 238 are not in contact with one another, and a gap 240may form between adjacent prongs 238. The method further includesdepositing solid metal particles forming agglomerations 232 over endportions/top portions 244 of the interdigitated prongs 238 and over aportion of the bus bar 230. The deposition may be also directed to andat least partially fill the one or more gaps 240. Additionally, anagglomeration 232 may cover one or more side edges of the prongs 238.The interconnects 234 may be formed as a single connected layer, such asan elongated stripe, or respective agglomerations 232 which are not incontact with each other. The method may include depositing theinterconnects 234 as one or more layers having varying dimensions,location, orientation, shape, the like, or a combination thereof. Anagglomeration 232 forming the interconnects 234 may be deposited overthe entire surface area of an interdigitated castellated tab 208 whichis in contact with the bus bar 230. Alternatively, only a portion of thetabs 208 overlapping the bus bar 230 may be covered with theagglomerated material 232. The amount of agglomerated material 232should be sufficient to ensure proper joining of the bus bar 230 withthe tabs 208, preventing detachment, while providing good electricalconnection. A mask may be utilized, as was described above.

A method of forming interconnects 334, depicted in FIG. 5, is furtherdescribed herein. The method includes providing a plurality of cells 300having tabs 308, which are characterized above. The method may includealigning the cells 300 and/or tabs 308 such as, for example, the topedges of the cells 300, the top and/or side edge(s) of the tabs 308, ora combination thereof, are flush with one another. The method includesplacing a first cell 300′ having a first tab 308′ in contact with thebus bar 330 such that a top portion/end portion 346 of the tab 308′overlaps a bottom portion of the bus bar 330. An agglomeration 332 ofsolid metal particles is then deposited over the tab 308′ and the busbar 330. The method includes placing a second cell 300″ having a secondtab 308″ over the first agglomeration 323′ and the first tab 308′ suchthat the second tab 308″ is in contact with the bus bar 330.Specifically, the second tab 308″ is in contact with the portion of thebus bar 330 which is located above the top edge of the firstagglomeration 323′. A third cell 300′″ having a third tab 308′ may bearranged in contact with the bus bar 330, the second agglomeration 323″,and the second tab 308″ in a similar fashion. Additional tabs 300 may beprovided, application of each additional tab 308 being followed bydeposition of an additional agglomeration 323. Layered or terracedinterconnects 234 are thus created. As was described above, the tabs 308may have a different width, height, and/or thickness, as long as theinterconnects 334 form a terrace 342. The dimensions of theagglomerations 332 between respective tabs 308 may have the same ordifferent dimensions, shape, location, orientation, the like, or acombination thereof.

The methods named above may include joining the same or different numberof cells to each side of a bus bar. More than one methods describedabove may be used to form interconnects of a single battery pack.

While the dielectric material and/or the interconnects of the modules100, 200, 300 may be formed by any type of cold spray depositiontechnique, a kinetic metallization process may provide a number ofadvantages. For example, the kinetic metallization process operates atsonic speeds and pressures of about 50 to 130 psig, which is lower thansome other cold spray methods which require up to 700 psig. The lowerpressure enables to perform the process while using smaller amount ofgas such as up to 1/10 of the gas needed in other types of cold spraymethods.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the disclosure. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the disclosure.

What is claimed is:
 1. A battery pack comprising: a pouch cell havingelectrode tabs extending therefrom, each of the tabs definingperforations extending into the tabs; a bus bar in contact with thetabs; and agglomerations of mechanically-bound solid metal particleseach filling one of the perforations, wherein the bus bar ismechanically bound and electrically connected to the tabs through theagglomerations.
 2. A battery pack comprising: a pouch cell havingelectrode tabs extending therefrom, each of the tabs definingperforations extending into the tabs; a bus bar in contact with thetabs; and agglomerations of mechanically-bound solid metal particleseach filling one of the perforations, wherein the perforations arecircular and have jagged perimeter edges.
 3. The battery pack of claim1, wherein the perforations are arranged in a regular pattern having anarray of at least three rows and three columns.
 4. A battery packcomprising: a pouch cell having electrode tabs extending therefrom, eachof the tabs defining perforations extending into the tabs; a bus bar incontact with the tabs; and agglomerations of mechanically-bound solidmetal particles each filling one of the perforations and covering atleast a portion of the tabs outside an outer perimeter of theperforations, the bus bar being mechanically bound and electricallyconnected to the tabs through the agglomerations.
 5. The battery pack ofclaim 1 wherein at least one perforation is partially filled with theagglomerations such that at least a portion of a perforation remainsfree of agglomerated material.
 6. The battery pack of claim 1 wherein anindividual agglomeration extends from a first perforation extending intoa first tab to a second perforation extending into the first tab.
 7. Thebattery pack of claim 1 wherein an individual agglomeration extendswithin an individual perforation, and wherein the individualagglomeration has a diameter greater than a maximum diameter of theindividual perforation.
 8. The battery pack of claim 1 wherein the tabsare castellated tab extending from the pouch cell.
 9. The battery packof claim 8 wherein castellated tabs are arranged adjacent to one anothersuch that the castellated tabs are aligned and interdigitate to contactthe bus bar.
 10. The battery pack of claim 8 wherein a first castellatedtab includes a pair of prongs.
 11. The battery pack of claim 8 whereinadjacent castellated tabs include prongs that are in contact with oneanother.
 12. The battery pack of claim 11 wherein the prongs of a firstcastellated tab have different dimensions than the prongs of a secondcastellated tab.